Turbo compressor

ABSTRACT

A turbo compressor includes a first compressor stage, which has a first compressor wheel, and a second compressor stage, which has a second compressor wheel, the first compressor wheel and the second compressor wheel being situated on a common shaft ( 12 ), the shaft being supported without contact. To reduce the complexity of the turbo compressor, a contactless bearing of the shaft is situated between the first compressor wheel and the second compressor wheel.

FIELD OF THE INVENTION

The present invention relates to a turbo compressor having a first and a second compressor stage. Each of the compressor stages has a compressor wheel, which is situated on a common shaft. The shaft is supported without contact.

BACKGROUND INFORMATION

Turbo compressors of the above-named type are believed to be understood in the related art. With the aid of multi-stage compressors, higher compression levels of a gaseous medium at a predefined volume flow may be achieved than when using simple compressors.

It is also believed to be understood to situate the compressor wheels of the corresponding compressor stages on a common shaft to reduce the quantity of parts.

Furthermore, it is believed to be understood that compressors for smaller volume flows must be operated at high rotational speeds. However, such high rotational speeds may entail problems with the bearing support of the movable parts, making it necessary in part to use complex bearings which are resistant to high rotational speeds. For such applications, it is known to use magnetic bearings .

However, magnetic bearings may have a number of disadvantages. They are complex to manufacture and are expensive, since on the one hand they require many components; on the other hand, they must be produced using the highest precision. Furthermore, they are difficult to adjust, so that their installation is also very complex. Another disadvantage of magnetic bearings is that their operation requires an electrical current, and bearing damage may occur in power failures.

A specific, device of the above-named type is a Danfoss Turbocor, which has a two-stage semi-hermetic centrifugal compressor and contactless magnetic bearings. Two impellers are situated on a common shaft without gears. The Danfoss Turbocor may be operated at a rotational speed range of 18,000 rpm to 48,000 rpm. The two impellers are situated roughly in an end one-fourth of a shaft extending axially. The shaft is supported with the aid of three magnetic bearings, two of which are radial bearings and one is an axial bearing. Such a bearing support is very complex and consumes much space.

SUMMARY OF THE INVENTION

An object of the present invention is thus to provide a turbo compressor of the above-named type, which has fewer components than conventional turbo compressors, is of a more compact configuration and is simpler to install and service.

This objective is achieved by a turbo compressor as described herein. Additional embodiments of the present invention are the subject matter of the further descriptions herein.

A turbo compressor according to the present invention has a first compressor stage which is equipped with a first compressor wheel. Such a compressor stage may be a radial compressor, an axial compressor, a cross-flow compressor or another compressor of a known type, which operates using rotating components.

The turbo compressor according to the present invention has a second compressor stage which is also equipped with a compressor wheel. Here also, it is possible to select from the different known basic principles. The second compressor stage is connected downstream from the first compressor stage, so that the, outlet of the first compressor stage is fluidically connected to the inlet of the second compressor stage.

The two compressor wheels of the first compressor stage and the second compressor stage are situated on a common shaft. The shaft is supported without contact.

According to the present invention, it is provided that a contactless bearing of the shaft is situated between the first compressor wheel and the second compressor wheel. The positioning of the contactless bearing between the two compressor wheels makes it possible on the one hand for axial forces on the bearing to be reduced; on the other hand, it makes it possible for the shaft to be shortened, since it is unnecessary for the bearing support of the shaft to be provided at least partially outside of the compressor stages.

According to a first possible embodiment of the turbo compressor according to the present invention, the contactless bearing may be a magnetic bearing. Magnetic bearings are well suited for the rotational speeds required in turbo compressors.

According to another possible embodiment of the present invention, it may be provided that the bearing between the first compressor wheel and the second compressor wheel is the only bearing for support of the shaft. The fact that compressor wheels are situated on both sides of the bearing makes it possible for the turbo compressor to be configured in such a way that the bearing must absorb only small transverse or shear forces and low axial forces, since the forces of the two compressor wheels which act on the shaft point in opposite directions and are mutually compensated.

Furthermore, this makes it possible to achieve a considerable reduction of the length of the shaft carrying the compressor wheels. This further reduces the inertia of the turbo compressor according to the present invention and consequently reduces the required starting energy.

According to another possible embodiment of the present invention, it may be provided that the first compressor wheel and the second compressor wheel are aligned with respect to one another in such a way that the respective inlets of the compressor stages are situated on diametrically opposed sides of the shaft . This may be achieved in particular by situating the compressor wheels back to back on the shaft. Such a positioning is moreover conducive to a simple installation or configuration of the turbo compressor according to the present invention having a small number of components.

Advantageously, the compressor wheels may also be formed in one piece with the shaft.

According to another embodiment of the present invention, it may be provided that the compressor wheels have essentially an equal distance to the bearing. In this way, transverse forces directed in a radial direction to the bearing are mutually compensated, so that the bearing is largely free of shear forces.

According to another possible embodiment of the present invention, the bearing may be configured as a combined, contactless radial and axial bearing. This makes it possible to achieve an even higher stability of the bearing, even in changing operating conditions of the turbo compressor.

According to another possible refinement of the present invention, the bearing may have a radially projecting flange on the shaft side, the flange being at least partly enclosed axially by housing-side bearing components. The housing-side bearing components may, for example, be magnets.

According to another possible embodiment of the present invention, an electrical drive and/or a generator may be integrated into the bearing. In this manner, the turbo compressor may be accelerated initially with the aid of an electric motor, and electrical energy may be obtained from the turbo compressor to make it possible, for example, to slow down the turbo compressor in a controlled manner in the case of a power failure without a failure of the contactless bearing.

According to another possible embodiment of the present invention, it may be provided that the shaft has a cavity, which is open on at least one side and is situated to be rotationally symmetric, a rotor being integrated into the cavity and a stator projecting into the cavity. In this manner, the stator is able to interact with the shaft without contact, and a combination is made possible of a contactless bearing, which normally interacts with the outer sides of the rotating part of the bearing connected to the shaft, and an electric motor of compact configuration.

According to another possible embodiment of the present invention, a point is provided which is situated on an axis of rotation of the shaft and has a distance to the shaft of 0 mm to 5 mm, which may be 0 mm to 1 mm. The point may be configured as a point of a cone. With the aid of such a point, it is possible to achieve an axial support of the contactless bearing, which only axially exerts a force on the shaft when the bearing is completely deflected from the equilibrium position, which may occur, for example, in load changes of the flowing medium. Such a point may also be situated on both sides of the shaft.

A first independent object of the present invention relates moreover to a shaft of a turbo compressor according to the above-described present invention. Such a shaft may thus support a bearing component of a contactless bearing as well as two compressor wheels which are situated to the left and right of the bearing component. The compressor wheels may be situated back to back. In addition to compressor wheels, the shaft may also have, referring to an axial center plane, a symmetrical system of compressor wheels and a bearing component. The bearing component may have a radially projecting flange. Furthermore, the shaft may have a cavity, in which a rotor of an electric motor is situated.

The compressor wheels and/or the bearing component may be formed in one piece with the shaft.

Additional objectives, advantages, features and possible applications of the present invention ensue from the following description of an exemplary embodiment with reference to the drawings. All described and/or graphically depicted features constitute the object of the present invention alone or in any arbitrary meaningful combination, also irrespective of their summary in the claims or their back-reference.

The present invention will be elucidated based on multiple exemplary embodiments.

In the following figures, components which are identical or have an identical function are provided with identical reference numerals for the sake of readability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a section through a two-stage turbo compressor according to the present invention according to a first variant.

FIG. 2 shows a section through a turbo compressor according to the present invention according to a second specific embodiment.

FIG. 3 shows a section through a turbo compressor according to the present invention according to a third specific embodiment.

FIG. 4 shows a section through a turbo compressor according to the present invention according to a fourth specific embodiment.

DETAILED DESCRIPTION

FIG. 1 shows a schematic section through a turbo compressor 2 according to the present invention. Turbo compressor 2 according to the present invention has a first compressor stage 4 and a second compressor stage 6. The first compressor stage has a first compressor wheel 8 and a second compressor wheel 10. First compressor wheel 8 and second compressor wheel 10 are formed in one piece with a shaft 12. Compressor wheels 8, 10 rotate about a common axis of rotation.

The common component, including shaft 12, first compressor wheel 8 and second compressor wheel 10, is supported with the aid of a magnetic bearing 14. Magnetic bearing 14 has a shaft-side bearing part 16 and a housing-side bearing part 18. An air gap 20 is located between the two bearing parts.

First compressor stage 4 has an inlet 22, through which the gaseous medium to be compressed flows into turbo compressor 2. The medium is accelerated to the outside by the first compressor wheel and is then compressed in a diffuser 24 and discharged radially to the outside. For that purpose, the first compressor stage is sealed toward the outside with the aid of a wall 26. A channel conducting media is formed on the outside with the aid of wall 26 and on the inside by housing-side bearing part 18 of magnetic bearing 14.

The precompresssed air is fed to an inlet 30 of the second compressor stage via an outlet 28 of the first compressor stage, and there it is accelerated a second time with the aid of second compressor wheel 10 and compressed with the aid of another diffuser 32. Lying radially outside in the second compressor stage, a channel having a wall 34 and housing-side bearing part 18 is also formed. The compressed medium exits second compressor stage 6 through an outlet 36.

Magnetic bearing 14 according to the present invention may simultaneously be formed as a motor, housing-side bearing part 18 then forming the stator and shaft-side bearing part 16 forming a rotor in this case.

According to FIG. 2, magnetic bearing 14 is, in contrast to the specific embodiment of FIG. 1, extended by a radially projecting flange 38 which is assignable to shaft-side bearing part 16. For this purpose, a groove 40 is provided in housing-side bearing part 18, flange 38 being situated within the groove. This configuration also stabilizes bearing 14 axially.

In the specific embodiment of FIG. 3, contactless magnetic bearing 14 is axially stabilized by a cone 42 which, including its point 44, is assigned to shaft 12. Point 44 lies essentially on the axis of rotation of shaft 12. Point 44 and shaft 12 are spaced very close to one another, which may be less than 1 mm. Shaft 12 and point 44 are thus only in contact when the shaft-compressor wheel unit is deflected axially. Cone 42 including its point 44 thus forms an axial support for the compressor according to the present invention.

In the specific embodiment according to FIG. 4, bearing 14 is configured as a pure bearing. A drive motor 46 for the two compressor stages 4, 6 is provided in shaft 12. For that purpose, shaft 12 has a coaxially situated cavity 48, in the interior of which a rotor 50 is situated. A likewise concentrically situated shaft 52 projects into cavity 48, stator 54 being situated on shaft 52. Motor 46 may also be used as a generator.

The List of reference numerals is as follows:

-   2 Turbo compressor -   4 First compressor stage -   6 Second compressor stage -   8 First compressor wheel -   10 Second compressor wheel -   12 Shaft -   14 Magnetic bearing -   16 Shaft-side bearing part -   18 Housing-side bearing part -   20 Air gap -   22 Inlet of the first compressor stage -   24 Diffuser -   26 Wall -   28 Outlet of the first compressor stage -   30 Inlet of the second compressor stage -   32 Diffuser -   34 Wall -   36 Outlet of the second compressor stage -   38 Flange -   40 Groove -   42 Cone -   44 Point -   46 Motor/generator -   48 Cavity -   50 Rotor -   52 Bar -   54 Stator 

1-11. (canceled)
 12. A turbo compressor, comprising: a first compressor stage having a first compressor wheel; a second compressor stage having a second compressor wheel; wherein the first compressor wheel and the second compressor wheel are situated on a common shaft, which is supported without contact, and wherein a contactless bearing of the shaft is situated between the first compressor wheel and the second compressor wheel.
 13. The turbo compressor of claim 12, wherein the contactless bearing is a magnetic bearing.
 14. The turbo compressor of claim 12, wherein the shaft is only supported with the aid of the contactless bearing.
 15. The turbo compressor of claim 12, wherein the first compressor wheel and the second compressor wheel are aligned so that the respective inlets of the compressor stages are situated on diametrically opposed sides of the shaft.
 16. The turbo compressor of claim 15, wherein the compressor wheels have essentially the same distance to the bearing.
 17. The turbo compressor of claim 12, wherein the bearing includes a combined, contactless radial and axial bearing.
 18. The turbo compressor of claim 17, wherein the bearing has a radially projecting flange on the shaft side, the flange being at least partly enclosed axially by housing-side bearing components.
 19. The turbo compressor of claim 12, wherein at least one of an electrical drive and a generator are integrated into the bearing.
 20. The turbo compressor of claim 19, wherein the shaft has a cavity, which is open on at least one side and is situated to be rotationally symmetrical, in which a rotor is situated, and a stator projecting into the cavity.
 21. The turbo compressor of claim 12, wherein a point is situated on an axis of rotation of the shaft and has a distance to the shaft of between 0 mm and 5 mm.
 22. The turbo compressor of claim 12, wherein a point is situated on an axis of rotation of the shaft and has a distance to the shaft of between 0 mm and 1 mm.
 23. A shaft, comprising: a first compressor wheel, a second compressor wheel and a contactless shaft-side bearing part of a contactless bearing of a turbo compressor; wherein the contactless shaft-side bearing part is situated between first compressor wheel and second compressor wheel, and wherein the turbo compressor includes a first compressor stage having the first compressor wheel, a second compressor stage having the second compressor wheel, the first compressor wheel and the second compressor wheel being situated on the shaft, which is supported without contact. 